CHAPTER XXII 



PRINCIPLES OF THE PHENOMENON OF COMPLEMENT 



FIXATION 



Historic. With Bordet's discovery of the hemolysins in 1898, 

 and his demonstration of the role of the antibody or sensitizer and alexin 

 in the process, new light was thrown upon the bacteriolysins, and the 

 close analogy between hemolysis and bacteriolysis soon became apparent. 

 Bordet's discoveries were quickly verified by Ehrlich and Morgenroth 

 and the German school in general, although his views regarding the 

 mechanism of the processes were questioned. The controversy soon 

 centered upon the question of the unity or the multiplicity of alexins 

 or complements. Bordet at this time advanced his belief in the existence 

 of one alexin or complement that would act with any sensitizer or ambo- 

 ceptor, and he still maintains this view. One of the experiments con- 

 ducted by him, and later made in conjunction with his pupil, Gengou, 

 in support of his theory, is now known as the Bordet-Gengou phenomenon 

 of complement fixation. This has become widely known as the precursor 

 of all complement-fixation tests, and is the basis of the well-known and 

 invaluable Wassermann reaction for the diagnosis of syphilis. 



In devising the technic of this important method, Bordet's main 

 object was to show that the complement in a normal serum would unite 

 with either a bacteriolytic or a hemolytic amboceptor, and that, by 

 furnishing sufficient of either amboceptor, all the complement may be 

 "fixed." He argued that if two or more complements existed in the 

 same serum, as was held by Ehrlich, they would demonstrate their 

 presence by exhibiting different affinities for these widely varying 

 amboceptors. 



Prior to this Bordet had shown that the addition of a small amount of 

 normal serum to an immune hemolysin would result in lysis of the homol- 

 ogous corpuscles, and that the process could not take place without the 

 alexin. He then mixed an emulsion of pest bacilli with antipest serum and 

 added a small amount of normal, unheated guinea-pig serum to supply 

 the alexin or complement. After allowing the mixture to stand for four 

 hours at room temperature, it was sought to determine whether the 

 alexin had been fixed by pest antigen and pest amboceptor, or whether 



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